Preliminary Remark—the “Background of the Invention” and the invention proper, will be described herein after in terms of an application related to agricultural water irrigation. However, any professional in this field would understand that the invention is not restricted solely to this domain, but rather the invention is also applicable to other uses, as for example wetting and flushing (rinsing) minerals with liquid detergent mixtures.
As is well known, irrigation systems [for example, dripping lines (extensions), sprinklers] are fed from water sources and deployed over large areas, that might include variable landscape features and various elevations (as e.g. slopes, hills, valleys and mountainous cultivated terraces). Hence, the water pressure as it arrives to an irrigation system and to the end units installed on them (for example—sprinklers), might be far from uniform as a result of variations in the water source pressure or pressure loss along the water supply lines, as well as due to topographic elevation differences. On the other hand optimal irrigation mandates a constants throughput (yield) values of all the end units of the systems that are deployed in the serviced area, and not a yield that might change due to variations in the pressure—for the reasons detailed above.
Hence, as is well known from the past there exist in the field, pressure regulator devices that are installed in irrigation systems in order to regulate the pressure differences that develop in the system. One such pressure regulator is described—for example, in Rosenberg's U.S. Pat. No. 5,339,860.
An additional problem that crops up in irrigation systems is the occurrence of leakage of the water remaining in the system after the water supply is cut off. Closing down the water supply source, leaves considerable quantities of water in the water supply lines and eventually it drains and leaks through the end units of the system that is located at a relative low height and the system has no water left in it. Obviously, this phenomenon necessitates that upon reopening the water source—water has to fill the system and its pressure builds up gradually—every time the irrigation starts anew. Naturally this results also in water loss and waste, combined with over watering at places that are relatively at low elevation compared to other plots being irrigated. Moreover—the problems worsens for crop being watered in the modern way—requiring timed watering with low time intervals and in accurate throughput every time.
As a result—several solutions incorporating pressure regulator devices in irrigation systems are known for some time. They include a no-drain valve that upon decreasing pressure in the supply system—prevent continued water leak through the regulator to the end units connected to it and whence out. Such pressure regulators are described for example in Ungerecht's et al U.S. Pat. No. 5,875,815 and Giordano's U.S. Pat. No. 6,820,643.
The problem with known existing regulators that include, as said—a no-drain valve, is that the no-drain valve is not given to independent control as well as that it is not possible to continue and have the water flow through the regulator when the pressure is lower than the planned (designed) regulating pressure. In these regulators, the opening and closing pressure of the no-drain valve is approximately identical to that of the regulating pressure, so that upon closing the water supply source the water flow decreases and with it the water pressure drops. The no-drain valve completely shuts off the water drainage. Hence the operation of these known regulators allows—for extended periods, existence of high residual pressure—a state that might enhance wear in the system's parts and components, e.g. the plastic water hoses. An additional problem that was detected in these regulators that include a no-drain valve is their large mechanical dimensions, as it evolves from the structure of the regulating piston that is implemented in them—that results in a large effective cross section area that is formed in a circumferential configuration (that naturally, increases the diameter of the regulator).
Thus—in the period that preceded the current invention, a need existed for pressure regulators fit to be used in irrigation systems that would include no-drain capabilities combined with being independently controllable (as much as the activity range of the no-drain valve is lower than or equal to the designed regulating pressure)—and that they would, simultaneously, be implemented having a compact structure, namely optimal small dimensions.